Westerbeke generator overheating

A few weeks ago I decided to so some PM on my generator which was in perfectly good working order. I removed the H/X and took it to a radiator shop to be cleaned out. Today I returned to the boat and after about 3 hours wrestling with hoses and clamps I finally got the dang thing back in.

"get me a beer" I say to the wife, "and crank the genny." It runs for about 5 minutes and the temp needle is firmly pegged on 100, then at once it jumps to > 180 and soon is somewhere near 200. It normally runs about 180. "Shut it down"

I have raw water flowing out of the side so that isn't the problem. Coolant level seems OK in the expansion reservoir. No leaks that I can see and no hoses are crimped. This is a round, 4 pass H/X and evidently is a pretty common design.

Documentation for WMD 4.4 is no help.

How can I tell if the fresh water pump is pumping? I tried running it for a short period with various hoses removed from the H/X and coolant isn't flowing, but I'm not 100% sure of this since I don't know which end of the H/X is the entry and which is the exit.

Could this be as simple as a stuck thermostat? System needs priming? Is there something the radiator shop could have done to render the H/X useless? I put in a new zinc and new gaskets/O rings on each end cap. Could removing the H/X for a few weeks cause such a failure? I have a hard time believing that the fresh water pump failed exactly when I chose to remove and clean the H/X. There are coincidences, but in my experience 99% of the time a problem like this is related to my activity.

Anything anyone can share would be appreciated. If I cannot get a lead as to what is wrong tomorrow I'm going to have to call a pro.

Woody

Look at the front of belt driven coolant pump. Good chance the pump is full of air. If there are any fittings on the upper part of the pump (such as temp switch, etc) loosen to bleed air. Also some exhaust manifolds have vent taps to bleed air. Also a vent tap on some thermostat housings, all on the top. Bleed and fill.

You can tell when coolant is circulating as hose going from exhaust manifold to HX will get hot when tstat opens.

Ski in NC said:

Look at the front of belt driven coolant pump. Good chance the pump is full of air. If there are any fittings on the upper part of the pump (such as temp switch, etc) loosen to bleed air. Also some exhaust manifolds have vent taps to bleed air. Also a vent tap on some thermostat housings, all on the top. Bleed and fill.

You can tell when coolant is circulating as hose going from exhaust manifold to HX will get hot when tstat opens.

Click to expand...

I feel a bit stupid... Just like you said, there was a vent tap on top of the exhaust manifold. Opened it up, started the generator, it bubbled for a while and I waited until coolant came out in a steady stream and then closed it back up. Now it runs at about 175 with no load, so cleaning the H/X was a good thing.

The only work the old Westerbeke has ever needed was a rebuilt raw water pump and oil and filter changes. This was my first time working with the fresh water system.

Thanks again!

OK guys and girls, back to the drawing board. Here's what is happening now:
I go down to the boat this weekend and I test start the generator and I notice the overflow tank is empty. I fill it up but the engine overheats. I let cool, open the bleed valve, run the motor until I get water shooting out, now the engine runs fine. I run it for 20 minutes or so and don't notice any overheating or leaking and the overflow tank is at the same level it was when I filled it. Maybe I have a leak?

Next day I go to use the generator for real and now the overflow tank is completely empty. I fill it to the top, bleed the system, and run the generator for a few hours. All is good and overflow level is the same. After a few hours not running the level went down by half. I start it up again, bleed the system, fill to the top and run for 12 hours, all good.

Something is leaking, but only when the generator is stopped. I've looked for leakage and can see none, but when I have time I'll run it and put fresh towels under it to see if I can spot where the leaking is. My best guess is that something expands when the generator is hot and that is stopping the leak.

Woody

Double check all of your hose clamps. is one stripped out or loose?

If that doesn't pan out then get yourself a radiator pressure tester. they aren't expensive or get a loaner from you local big box autoparts store. If all is quiet and still you should be able to hear/see your leak.

Radiator cap

Remember the radiator cap is an integral part of your coolant system. It controls the flow in and out of your overflow tank. I had a faulty one on my Perkins and it would allow the overflow tank to drain down when the engine was not in use. The cap seals in several places and in different directions depending on pressure or vacuum present in the engine block.

I reread what you posted and you mention that the expansion tank is empty...how is the level in the heat exchanger? another possibility is that it is leaking from the expansion tank or the tube between it and the heat exchanger.

Some of the smaller westies the cooling system must be dang near solid with coolant.

Also, the port from the recovery bottle nipple to the expansion tank cap neck is prone to plug with corrosion. Make sure that port is clear. With cap off, fluid should move from nipple into cap neck.

Also, best for these to have the recovery bottle fluid level above level of pressure cap. That way coolant never has to be sucked back into system, gravity will do it. If recovery bottle is a foot or more below, then it is possible for air voids to form in engine system and these are sensitive to that.